Weeds compete with plum trees for light, nutrients, and water. Weed interference can be minimized with proper cultural practices and herbicides. General maintenance, such as controlling weeds in adjacent areas (i.e., nearby fields, ditches, and driving paths), preventing weeds from producing seeds, and cleaning mowing equipment of weed seed, will prevent weeds from becoming a serious problem. Cultivation can be used but should be shallow to prevent root pruning and soil erosion.

Chemical Control

Herbicides available for weed control in plums are included in Tables 1 and 2. Table 1 lists herbicides that control weeds before they emerge (preemergence). Table 2 lists herbicides that control weeds after they emerge (postemergence). Because soil types in Florida vary, consult the labels for application rate restrictions based on soil type. Bearing trees are plum trees that are currently producing fruit. Nonbearing trees are plum trees that will not produce fruit for a year after application. The table includes preharvest intervals (PHI) and restricted-entry intervals (REI).

Practices for improving weed control with herbicides are as follows:

Herbicide selection. Preemergence herbicides control weeds before they emerge from the seed or soil surface. Postemergence herbicides control weeds that have emerged through the soil surface.

Optimal timing. Preemergence herbicides should be applied in the early spring or fall before annual weeds emerge. Postemergence herbicide efficacy decreases as weeds grow. Consult the label for the correct size of weed to control.

Sufficient coverage. Herbicide labels require certain gallons per acre (GPA) or nozzle types for proper coverage. Before spraying, check that all nozzles have a correct spray pattern and correct output.

Herbicide Resistance

Herbicide-resistant weeds are a continuous and growing concern for farmers. Methods for reducing the chances of herbicide resistance include the following:

Rotate herbicide's mode of action. Each herbicide's mode of action (MOA) has been assigned a numerical group. Tables 1 and 2 list the MOA for each herbicide. Rotate between modes of action/numerical groups.

Include multiple MOA. Many herbicides allow for tank mixing herbicides. It is often suggested that preemergence herbicides be tank mixed with a postemergence herbicide. This method controls weeds that will emerge as well as weeds that have already emerged.

Managing known resistance. If an area of the field is known to have a resistant weed species, use mechanical weed removal to prevent the weed from producing seeds or other methods of propagation. Please contact your county Extension agent to have the weed resistance confirmed and documented.

Tables

Table 1.

Preemergence weed control in plum

Common name

lb. a.i. / A

(Trade name) formulation

amount of product / A

Weeds controlled

Flumioxazin, MOA 14

0.19–0.38

(Chateau®) 51 WDG

6–12 oz.

Broadleaf and annual grass weeds

Remarks: Bearing and nonbearing trees. In soils with sand plus gravel content greater than 80%, do not apply more than 6 oz./A per application to trees less than 3 years of age. Do not apply more than 24 oz./year. Best results if applied as a split application with a minimum of 30 days between applications. Avoid direct or indirect spray contact with foliage and green bark. Do not apply after flowering unless using a shielded sprayer. Do not apply to trees established less than 1 year unless protected from spray contact by nonporous wraps, grow tubes, or waxed containers. Tank mix with burndown herbicides. PHI 60 days. REI 12 hours.

Isoxaben, MOA 12

0.5–1.0

(Gallery®, Gallery® T&V) 75 DF

0.66–1.33 lb.

Certain broadleaf weeds

Remarks: Nonbearing trees. Direct spray solution to the base of the tree. A rainfall or irrigation of 0.5 in. or more within 21 days after application is required for activation. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. REI 12 hours.

Isoxaben, MOA 12 + Oryzalin, MOA 3

2.0–4.0 +

0.5–1

(Snapshot®) 2.5 TG

100–200 lb.

Certain broadleaf and annual grass weeds

Remarks: Nonbearing trees. Apply with a drop or rotary spreader. Requires 0.5 or more in. of rainfall or irrigation within 3 days of application for activation. Do not apply more than 600 lb./A per year. REI 12 hours.

Norflurazon, MOA 12

0.98–1.18

(Solicam®) 80 WDG

1.25–1.50 lb.

Small-seed broadleaf and annual grass weeds

Remarks: Bearing and nonbearing trees. Do not apply until trees are 1 year old. Temporary loss of pigment (whitening) in leaf veins may occur with normal use. Rainfall or irrigation is required within 4 weeks of application. Consult label for postemergence herbicides that can be tank mixed to broaden spectrum of weed control. Can be applied as a sequential application, but do not exceed 2.5 lb. product/A per year. Do not apply within 60 days of harvest. REI 12 hours.

Oryzalin, MOA 3

2–6

(Oryzalin, Surflan®) 4 AS

2–6 qt.

Certain annual broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Apply as a sequential treatment with 2.5 months between applications. Do not exceed 12 lb. a.i./A per year. An irrigation or rain event of 0.5–1 in. is required within 1 week of application. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. REI 24 hours.

Oxyfluorfen, MOA 14

1.25–1.5

(Goal® 2XL, Galigan®) 2 EC

5–8 pt.

(Goaltender®) 4 E

2.5–4 pt.

Broadleaf weeds

Remarks:Bearing and nonbearing trees. Apply after dormancy is initiated and before bud break. Broadcast application is 1.25–1.5 lb. a.i./A, and banded treatment is 1.25–2 lb. a.i./A. Do not apply more than 1.5 lb. a.i./A per year in broadcast applications and 2 lb. a.i./A per year in banded applications. Direct spray solution to the base of the tree using a shielded sprayer. Requires 0.5–2 in. of rainfall or irrigation within 3–4 weeks of application for activation. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. REI 24 hours.

Pendimethalin, MOA 3

1.9–6.0

(Prowl® H2O) 3.8

2.0–6.3 qt.

(Prowl®, Pendulum®) 3.3 EC

2.3–7.3 qt.

Broadleaf and grass weeds

Remarks: Nonbearing trees. Direct spray solution to the base of the tree. Apply during the dormant period. Apply as a single application or sequential application with 30 days between applications. After application, 1–2 in. of rainfall or irrigation are required for activation. For newly transplanted trees, apply after a rain or irrigation event settles soil around the roots. PHI 90 days. REI 24 hours.

Pronamide, MOA 3

1–2

(Kerb®) 50 W

2–4 lb.

Certain broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Do not apply until 1 year after fall transplanting or 6 months after spring transplanting. Direct spray solution to the base of the tree after fruit harvest. Apply in the fall when temperatures are below 55°F and before soil freezes. Do not apply more than 4 lb. a.i./A or one application per year. REI 24 hours.

Rimsulfuron, MOA 2

0.03–0.06

(Matrix® FNV, Matrix® SG) 25 WG

2–4 oz.

Certain broadleaf weeds and annual grasses

Remarks: Bearing and nonbearing trees. Apply after trees are 1 year old. Broadcast application is limited to one application per year at 4 oz./A. Banded application may be applied twice a year with 30 days between applications not to exceed 4 oz./A per year. Direct spray solution to the base of the tree, avoiding contact with foliage or fruit (except undesirable suckers). Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. Do not apply within 14 days of harvest. REI 4 hours.

Simazine, MOA 5

1.6–4

(Princep®, Simazine) 90 WDG

1.6–4.4 lb.

(Princep®, Simazine) 4 L

1.6–4 qt.

Annual broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Do not apply more than 4 lb. a.i./A per calendar year. Do not make more than one application per year. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. REI 48 hours.

Terbacil, MOA 5

0.4–1.6

(Sinbar®) 80 WP

0.5–2 lb.

Annual broadleaf and grass weeds

Remarks: Nonbearing trees. Apply to newly transplanted trees after a significant rainfall or irrigation that will allow soil to settle around the tree base. Make one to twoapplications per season, and do not exceed 1 lb./A. Do not apply to soils containing less than 1% organic matter. Approximately 0.5–1.0 in. of rainfall or irrigation is required within 2 weeks of application. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. REI 12 hours.

Trifluralin, MOA 3

0.5–2

(Triflurex®, Treflan®, Trust®) 4 EC

1–4 pt.

(Treflan®, Trust®) 10 G

5–20 lb.

Annual broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Apply 0.5–0.75 lb. a.i./A for newly transplanted trees after soil has settled. Apply 1–2 lb. a.i./A for established trees. Within 3 days of application, 0.5–2 in. of rainfall or irrigation are required for activation. Consult label for restriction based on soil type. PHI 60 days. REI 12 hours.

Table 2.

Postemergence weed control in plum

Common name

lb. a.i. / A

(Trade name) formulation

amount of product / A

Weeds controlled

2,4-D, MOA 4

(Various formulations)

Broadleaf weeds

Remarks: Bearing and nonbearing. Consult individual labels for amount of formulation to include in spray solution. Do not apply during bloom. Trees must be at least 1 year old. Prevent drift from contacting foliage, fruit, stems, and trunks of the tree. Withhold irrigation 2 days before irrigation and 3 days after application. Do not apply more than 2 lb. a.i./A per application, and do not make more than two applications in a growing season. Allow 75 days between applications. Do not apply within 40 days of harvest. REI 48 hours.

Carfentrazone, MOA 14

Up to 0.031

(Aim®) 2 EC

Up to 2.0 fl. oz.

(Aim®) 1.9 EW

Up to 2.0 fl. oz.

Broadleaf weeds

Remarks: Apply to bearing and nonbearing trees. Consult label for appropriate rate based on weed species. Do not apply more than 0.124 lb. a.i/A in a growing season. Apply with hooded sprayer direct to the base of the tree to reduce contact with green stem tissue, desirable fruit, blooms, and foliage. Applications must be 14 days apart. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. For control of undesirable suckers at the base of the tree, apply at 0.031 lb. a.i./A. Suckers must be young and not mature. For all types of applications, include a nonionic surfactant at 0.25% v/v or crop oil concentrate at 1% v/v.Do not apply within 3 days of harvest. REI 12 hours.

Clethodim, MOA 1

0.14–0.25

(Arrow®, Select®) 2 EC

6–8 fl. oz.

(Select Max®) 1 EC

9–16 fl. oz.

Annual and perennial grass weeds

Remarks: Nonbearing trees. Include a nonionic surfactant at 0.25% v/v. Direct the spray to the base of the tree. REI 24 hours.

Clopyralid,MOA 4

0.12–0.25

(Clopyr AG) 3 EC

0.33–0.66 pt.

Broadleaf weeds

Remarks: Bearing and nonbearing trees. Do not exceed 0.25 lb. a.i./A in a single application. Apply one to two broadcast applications per year. Do not apply within 30 days of harvest. REI 12 hours.

Diquat, MOA 22

0.7–0.9

(Diquat) 2 L

1.5–2.0 pt.

Broadleaf and grass weeds

Remarks: Nonbearing trees. Direct spray to the base of the tree to minimize contact with green stems and foliage. Include a nonionic surfactant at 0.06%–0.5% v/v. REI 24 hours.

Flumioxazin, MOA 14

0.19–0.38

(Chateau®) 51 WDG

6–12 oz.

Broadleaf and annual grass weeds

Remarks: Nonbearing trees. A maximum of 6 oz./A per application in soils that have a sand plus gravel content greater than 80% on trees less than 3 years of age. Do not apply more than 24 oz./year. Best results if applied as a split application with a minimum of 30 days between applications. Avoid direct or indirect spray contact to foliage and green bark. Do not apply after flowering unless using a shielded sprayer. Do not apply to trees established less than 1 year unless protected from spray contact by nonporous wraps, grow tubes, or waxed containers. Tank mix with burndown herbicides. Include nonionic surfactant at 0.25% v/v or crop oil concentrate at 1 qt./A. PHI 60 days. REI 12 hours.

Fluazifop, MOA 1

0.25–0.38

(Fusilade® DX) 2 EC

16–24 fl. oz.

Annual and perennial grass weeds

Remarks: Bearing and nonbearing trees. Direct spray solution to the base of the trees to minimize contact with leaves. Do not apply more than 72 fl. oz./A per season. Include nonionic surfactant at 0.25%–0.5% v/v or crop oil concentrate at 1% v/v. PHI 14 days. Do not apply when harvestable fruit are on the ground. REI 12 hours.

Glyphosate, MOA 9

(Various formulations)

Broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Glyphosate has various formulations. Consult individual labels for rates. Do not exceed 9.6 lb. a.i./A in a single season. Direct spray solution to the base of the tree to minimize contact with desirable vegetation. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. PHI 17 days. REI 4 hours.

Oxyfluorfen, MOA 14

0.5–1.5

(Goal®2XL, Galigan®) 2 EC

2–8 pt.

(Goaltender®) 4 E

1–4 pt.

Broadleaf weeds

Remarks: Lower rates for weeds up to the four-leaf stage and higher rates for weeds up to the six-leaf stage. Do not apply more than 1.5 lb. a.i./A per year in broadcast applications and 2 lb. a.i./A per year in banded applications. Direct spray solution to the base of the tree using a shielded sprayer. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. Include a nonionic surfactant at 2 pt. per 100 gal. of solution. REI 24 hours.Re

Paraquat, MOA 22

0.63–1

(Gramoxone Inteon®) 2 SL

2.5–4 pt.

(Firestorm®) 3 SL

1.7–2.7 pt.

Broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Use a shielded sprayer or wrap plants when spraying around young trees. Direct spray to the base of the trees to minimize drift to foliage, flowers, and fruits. Do not make more than three applications per year. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. PHI 28 days. REI 12 hours.

Pelargonic Acid

(Scythe®)

3%–10% v/v

Broadleaf and grass weeds

Remarks: Bearing and nonbearing trees. Contact herbicide that should be applied with a shielded sprayer and direct sprayed to the base of the tree to minimize contact with foliage and green bark. Consult label for control of suckers. Should be tank mixed with preemergence herbicide to broaden spectrum of weed control. REI 12 hours.

Rimsulfuron, MOA 2

0.03–0.06

(Matrix® FNV, Matrix® SG) 25 WG

2–4 oz.

Certain broadleaf weeds and annual grasses

Remarks: Bearing and nonbearing trees. Apply after plants are 1 year old. Broadcast application is limited to one application per year at 4 oz./A. Banded application may be applied twice a year with 30 days between applications not to exceed 4 oz./A per year. Use a nonionic surfactant at 0.125% v/v. Direct spray solution to the base of the tree, avoiding contact with foliage and fruit (except undesirable suckers). Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. PHI 14 days. REI 4 hours.

Sethoxydim, MOA 1

0.3–0.5

(Poast®) 1.5 EC

1.5–2.5 pt.

Annual and perennial grass weeds

Remarks: Nonbearing trees. Include crop oil concentrate at 2 pt./A or methylated seed oil at 1.5 pt./A. Do not apply more than 2.5 pt./A in a single application. Do not exceed 5.0 pt./A per season. Consult label for herbicides that can be tank mixed to broaden spectrum of weed control. PHI 25 days. REI 12 hours.

Footnotes

1.

This document is HS96, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 1993. Revised February 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.